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Message-ID: <yq1a77oc56s.fsf@oracle.com>
Date: Thu, 19 Dec 2019 17:37:47 -0500
From: "Martin K. Petersen" <martin.petersen@...cle.com>
To: Kirill Tkhai <ktkhai@...tuozzo.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>, axboe@...nel.dk,
linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-ext4@...r.kernel.org, tytso@....edu,
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andrea.parri@...rulasolutions.com, hare@...e.com, tj@...nel.org,
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chaitanya.kulkarni@....com, bvanassche@....org,
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Subject: Re: [PATCH RFC 1/3] block: Add support for REQ_OP_ASSIGN_RANGE operation
Kirill,
> Hm. BLKDEV_ZERO_NOUNMAP is used in __blkdev_issue_write_zeroes() only.
> So, do I understand right that we should the below two?:
>
> 1) Introduce a new flag BLKDEV_ZERO_ALLOCATE for
> blkdev_issue_write_zeroes().
> 2) Introduce a new flag REQ_NOZERO in enum req_opf.
Something like that. If zeroing is a problem for you.
Right now we offer the following semantics:
Deallocate, no zeroing (discard)
Optionally deallocate, zeroing (zeroout)
Allocate, zeroing (zeroout + NOUNMAP)
Some devices also implement a fourth option which would be:
Anchor: Allocate, no zeroing
> Won't this confuse a reader that we have blkdev_issue_write_zeroes(),
> which does not write zeroes sometimes? Maybe we should rename
> blkdev_issue_write_zeroes() in some more generic name?
Maybe. The naming is what it is for hysterical raisins and reflects how
things are implemented in the storage protocols. I wouldn't worry too
much about that. We can rename things if need be but we shouldn't plumb
an essentially identical operation through the block stack just to
expose a different name at the top.
--
Martin K. Petersen Oracle Linux Engineering
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